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Image forming apparatus and image forming methodImage forming apparatus and image forming method description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070247680, Image forming apparatus and image forming method. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a Continuation of U.S. application Ser. No. 10/392,302, filed Mar. 20, 2003, which claims the benefit of priority from the prior Japanese Patent Application No. 2002-100483, filed Apr. 2, 2002, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an image forming apparatus, in particular relates to an image forming apparatus and an image forming method, in which a gamma correction table is updated with a simple way. [0004] 2. Description of the Related Art [0005] Recently various modes of image forming apparatus are developed, manufactured and widely spread as image information is treated as digital information. In such an image forming apparatus, it is desirable to further increase image quality, a gamma correction table is provided in order to correspond to a change in characteristics of a scanner portion, a printer portion and the like, and the image information is corrected with the gamma correction table to perform the image formation in order to correspond to the change in characteristics. [0006] With reference to the image forming apparatus of the prior art, in generation of the gamma correction table, a gradation pattern stored in a storage area in the apparatus is printed, the printed gradation pattern is read by the scanner, and the gamma correction table is generated and updated on the basis of a result which has been read by the scanner. Accordingly, a result of the desired and high-quality image formation can be obtained with the correction in which physical characteristics of the scanner portion, the printer portion and the like are reflected at that time. [0007] However, operation, in which a printed sheet of the gradation pattern having the built-in gradation pattern printed therein as described above is moved by a user to a scanner table to be read with the scanner, is at least generated in the update processing of the gamma correction table in the apparatus of the prior art. In addition, the operation for changing a normal operation mode to the gamma correction table update mode is also required. Thus, since the update processing of the gamma correction table in the apparatus of the prior art is burdensome for the user, and is not performed periodically and automatically, when the user neglects the update processing of the gamma correction table, there is a problem that it is not always possible to perform the high-quality image formation. BRIEF SUMMARY OF THE INVENTION [0008] It is an object of the invention to provide an image forming apparatus and an image forming method, in which high-quality image formation applying easily an optimum gamma correction table can be performed by automatically updating the gamma correction table in the image forming apparatus. [0009] In order to achieve the above object, according to an aspect of the present invention, there is provided an image forming apparatus comprising: a pattern forming portion which reads gradation pattern information stored in a predetermined storage area and forms an image according to the gradation pattern information on an image recording medium; a first generating portion which reads the image according to the gradation pattern information on the image recording medium formed by the pattern forming portion by using a scanner, and generates a first gamma correction table on the basis of the read image information; a first printing portion which reads the gradation pattern information stored in the predetermined storage area, corrects the gradation pattern according to the first gamma correction table generated by the first generating portion, and prints an image according to the corrected gradation pattern information on an image carrier; a storage portion which detects a density of the image printed on the image carrier by the first printing portion, with a sensor for the amount of adhered toner, and stores the density of the image as a reference value of density in a storage area; a second printing portion which reads the gradation pattern information stored in the given storage area at an arbitrary timing, corrects the gradation pattern information with the first gamma correction table generated by the first generating portion, and prints an image according to the corrected gradation pattern information on the image carrier; a calculating portion which detects the density of the image printed on the image carrier by the second printing portion, with the sensor for the amount of adhered toner, compares the density of the image to the reference value of density stored in the storage portion, and calculates density deviation; a second generating portion which generates a newly second gamma correction table on the basis of the density deviation which the calculating portion has calculated; and an image forming portion which reads image information on an original with the scanner, corrects the read image information with the gamma correction table formed by the second generating portion, and forms an image based on the corrected image information on the image recording medium. [0010] As described above, the image forming apparatus of the invention decides the gamma correction table by printing and reading once the gradation pattern similarly to the apparatus of the prior art. Then, the gradation pattern is printed on an image carrier such as a drum and density is stored as reference density D.sub.R. However, thereafter, the gradation pattern is printed on the image carrier such as the drum and the density D is detected in the same way at a predetermined arbitrary timing, e.g., daily start-up of a copying machine or every three hours in continuous use of the copying machine. The previously recorded reference density D.sub.R is compared to the detected density D to determine density deviation .DELTA.D, and the gamma correction table is automatically updated according to the density deviation .DELTA.D. Consequently, the user can automatically update the optimum gamma correction table at the set timing without performing any special operation. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING [0011] FIG. 1 is a flow chart schematically showing an example of automatic update processing of a gamma correction table according to the invention; [0012] FIG. 2 is a sectional view showing an example of a structure of an image forming apparatus according to the invention; [0013] FIG. 3 is a block diagram showing an example of a configuration of the image forming apparatus according to the invention; [0014] FIGS. 4A and 4B are flow charts illustrating in detail an embodiment of the automatic update processing of the gamma correction table according to the invention; [0015] FIGS. 5A and 5B are flow charts illustrating in detail an example of the automatic update processing of the gamma correction table according to the invention; [0016] FIG. 6 is a flow chart illustrating in detail an example of the automatic update processing of the gamma correction table according to the invention; [0017] FIG. 7 is a graph for illustrating definition of each axis of the graph illustrating the automatic update processing of the gamma correction table according to the invention; [0018] FIG. 8 is a graph showing image density of a sample in which a gradation sheet for gamma correction is printed by a printer regarding the automatic update processing of the gamma correction table according to the invention; [0019] FIG. 9 is a graph showing reflectivity regarding the automatic update processing of the gamma correction table according to the invention when the gradation sheet for gamma correction is read by a scanner; [0020] FIG. 10 is a graph showing a case in which the reflectivity is transformed into an area ratio regarding the automatic update processing of the gamma correction table according to the invention; Continue reading about Image forming apparatus and image forming method... Full patent description for Image forming apparatus and image forming method Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Image forming apparatus and image forming method patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Image forming apparatus and image forming method or other areas of interest. ### Previous Patent Application: Workflows for color correcting images Next Patent Application: Method for correcting scanner non-uniformity Industry Class: Facsimile and static presentation processing ### FreshPatents.com Support Thank you for viewing the Image forming apparatus and image forming method patent info. 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